1. Field of the Invention
The present invention relates to an improved semiconductor device having multiple output terminals, and an improved method and apparatus for testing the same.
2. Description of the Related Art
An LSI tester is generally used for a test such as a selection of LSIs. In conventional techniques, in order to test an LSI, the tester must have terminals corresponding to the number of terminals of an LSI. When the number of terminals of the tester is less than that of the LSI, the LSI can be tested by banding terminals to be tested (terminals of an LSI) and using a relay or the like.
FIG. 1 shows, as a conventional method for testing, a basic structure for testing an LSI by banding the terminals to be tested using a relay. In FIG. 1, reference numeral 101 denotes an LSI; and 102, a tester. Reference symbols I.sub.n (n=1, 2, . . . ) denote inverted signals of data output to output terminals; SW.sub.n (n=1, 2, . . . ), relays inserted between the LSI and the tester; O.sub.n (n=1, 2, . . . ), output terminals of the LSI; and E.sub.n (n=1, 2, . . . ), signals supplied to the tester.
Each pair of outputs O.sub.n of the LSI 101 are commonly connected through a corresponding one of the relays SW.sub.n, and each common connecting point is connected to a corresponding one of the measuring terminals of the tester 102. For this reason, the LSI 101 having output terminals, the number of which is larger than the number of measuring terminals of the tester 102, can be tested. All the output terminals O.sub.n can be tested by switching the relays. At this time, the signal E.sub.m (m=1, 2, . . . ) supplied to the tester 102 corresponds to I.sub.(2m-1) when the relay SW.sub.(2m-1) is set in an ON state and the relay SW.sub.2m is set in an OFF state. When the relay SW.sub.(2m-1) is set in an OFF state and the relay SW.sub.2m is set in an ON state, the signal E.sub.m corresponds to I.sub.2m.
However, along with the advance of semiconductor techniques, an LSI is highly integrated, and an increase in number of terminals of the LSI is conspicuous. On the other hand, the development of a tester for testing the above LSI cannot cope with an increase in the number of terminals of the LSI, and a large-sized device is required. For this reason, the production cost is increased. As described above, when a test is performed by using a relay or the like and banding the terminals to be measured, depending on the increase of terminals in the LSI, the number of measuring terminals of the tester is increased, the capacity of a relay and the characteristics and reliability of the test are degraded, and wirings are complicated.